Ligand Free One-Pot Synthesis of Pyrano[2,3-c]pyrazoles in Water Extract of Banana Peel (WEB): A Green Chemistry Approach

Abstract

Here, we have developed a novel, simple, efficient, and green protocol for one-pot synthesis of pyrano[2,3-c]pyrazole using arylidene malononitrile and pyrazolone in Water Extract of Banana Peels (WEB) as a reaction medium at room temperature (r.t.). This is a green and general synthetic protocol without utilization of any toxic organic solvent, ligand, base that could be applicable for the wide substrate scope in good to excellent yields. This protocol has various advantages such as fast reactions, eco-friendly reaction conditions, easy isolation of the product without using column chromatography. The green chemistry matrices calculation like atom economy reaction, environmental factor, as well as process mass intensity indicates the eco-friendly nature of the protocol.

Ultrasound-assisted transition-metal-free catalysis: a sustainable route towards the synthesis of bioactive heterocycles

“…The synthesis of these compounds where several heterocycles are combined in such a way that leads to the formation of new single molecules from easily available simple starting materials has recently received considerable attention from chemists and pharmacologists for the outstanding properties of the targeted compounds. [180][181][182] The development in this regard realizes the outstanding contribution of Seydimemet et al to the expedient synthesis of a plethora of coumarin-containing pyrano[2,3-c]pyrazoles by introducing the sonochemical activation strategy under organocatalytic conditions (Scheme 37). 183 Under the inuence of 10 mol% of L-proline, the one-pot domino reaction of bketoesters 132 with phenylhydrazine 133, aromatic aldehydes 5, and active methylene 96 in ethanol was carried out in sonication, which provided the respective products 134 in 78-90% yield aer 50 minutes.…”

“…Among them, dihydropyrano[2,3-c]pyrazole is a well established fused heterocycle synthesized from pyrazolone, which displays various pharmacological properties like anti-bacterial, anti-HIV, insecticidal, anti-infective, antiplatelet, anti-fungal, anti-cancer, anti-microbial, antioxidant, analgesic activity, etc. 79,181,186,187 Due to the above mentioned pivotal signicance of pyrano [2,3-c]pyrazoles, Kotha and his co-workers demonstrated an atom-economic approach for the rapid access to a library of pyrano[2,3-c]pyrazoles 142 from a three-component ultrasoundassisted reaction of aldehydes 23, malononitrile 96, and pyrazolone 141 in aqueous ethanolic solution (1 : 1, v/v) at room temperature using sodium uoride (NaF) as the base catalyst (Scheme 40). 188 A diverse range of aryl aldehydes bearing different substituents were efficiently worked by this method, and overall, 12 target compounds have been accomplished in 88-98% yield within only 5-10 minutes.…”

4‐Hydroxycoumarin: A Versatile Substrate for Transition‐metal‐free Multicomponent Synthesis of Bioactive Heterocycles

“…Pyrazolones/pyrazoles and their derivatives constitute an important class of nitrogen-containing heterocyclic compounds that have received immense interest over the last decades due to their wide-ranging application in many branches of chemistry including synthetic organic chemistry, material science, medicinal chemistry, food industry, textile biologically active heterocycles industry, cosmetics products, chemical industry. [54][55][56][57] Interestingly, the incorporation of pyrazolone/ pyrazole moiety into bioactive coumarins now leads to a vast array of biologically active synthetic targets and tremendous growth has been witnessed in the past decades.…”

Applications of pyrazolone in multicomponent reactions for the synthesis of dihydropyrano[2,3-c]pyrazoles and spiro-pyrano[2,3-c]pyrazoles in an aqueous medium

“…However, several advantages such as mild reaction conditions, environmentally friendly nature, operational simplicity, low cost, an excellent yield of the product make this methodology very attractive for future application in organic synthesis (Scheme 69). 121 In this reaction WEB plays an important role both as the catalyst as well as a solvent without using any other ligand, base, metal additives, acid, etc. 122 All aromatic, heteroaromatic as well as aliphatic aldehydes, ketones were smoothly undergoing the reaction in the successful transformation to the corresponding product.…”